scope:

This standard specifies preferred frequencies for acoustical measurements. The preferred frequencies are based on the R10 series of preferred numbers in ISO 3. For most acoustical measurements and presentations of data a frequency spacing based on a constant percentage increment is generally preferred and the test frequencies then form a geometric series. For certain acoustical measurements, however, a constant frequency increment is a suitable spacing. This standard deals with the geometric series and is not intended to apply to cases where a constant frequency increment, or other particular spacing, would be more suistable, or where there may be good reasons for the adoption or retention of other frequencies.